The present work has been performed on a intensive swine farm containing a slurry treatment system. This consists of a thickener decantator working by gravity, and a facultatively anaerobic tank with 30 days of retention time. The final effluents are used in agriculture as fertilizers. The aim of this work is to determine the concentration of metals in decanted swine slurry and sludge, as well as to evaluate the ecotoxicity of the fraction with highest risk for the environment.We have used the following methods: Ca, Mg, Ni, Cr, Co, Cu, Mn, Zn and Fe by atomic absorption spectrometry; Na and K by flame photometry; EC 5 0 by luminescence bioassay.The ratio of metals in sludge/metals in decanted slurry ranges between 2 in the case of Ni and 270 for the Zn. Therefore, the metal concentration is higher in the sludge. We have found EC 5 0 ranging from 5.200 and 45.750 mg/l, therefore its use in agriculture has to be checked because of the possible metal accumulation in soils.